Ship emissions impact on Danish air quality

A revised Gothenburg protocol is expected to include new national emission ceilings for 2020.

Ship emissions of sulphur dioxide (SO2) in Danish waters are expected to come down by more than 90 per cent between 2007 and 2020, as a result of the strengthened sulphur requirements adopted by the International Maritime Organisation (IMO) in October 2008.

On the other hand, emissions of nitrogen oxides (NOx) are expected to rise by either fifteen or two per cent in the same time period – the lower figure could be achieved provided that the Baltic Sea and the North Sea become Emission Control areas (ECAs) for NOx. The increasing NOx emissions result from the fact that the weak IMO requirements for NOx are more than outweighed by the expected growth in shipping traffic.

The figures come from a study1 by the National Environmental Research Institute (NERI), prepared for the Danish Ministry of the Environment.

Concerning the amount of ship traffic, an annual increase of 3.5 per cent has been assumed for transport of goods from 2011 and onwards, while passenger traffic is assumed unchanged. Fuel consumption is projected to increase by 15 per cent.

Ships’ contribution to air pollutant concentrations in Denmark was also calculated. Between 2007 and 2020, the share from ships is expected to come down from 37 to 10 per cent for SO2, while it is expected to increase from 21 to 34 per cent for NO2, and from 18 to 24 per cent for modelled fine particles (PM2.5).

The concentration of nitrogen dioxide (NO2) in urban background air in Copenhagen is expected to be lowered from 16 to 9 micrograms per cubic metre (µg/m3) in the period up to 2020. This improvement is due to reductions in NOx emissions from land-based sources. If assuming that ECA-requirements will apply from 2016, the absolute contribution from shipping remains essentially unchanged. However, the relative contribution from ship traffic to the urban background concentrations is expected to increase from 12 to 21 per cent between 2007 and 2020.